1. Field of the Invention
This invention relates to solar batteries of the type having a board with a surface and a plurality of spherical segments projecting from the board surface. The invention is also directed to a method of treating a board for a solar battery.
2. Background Art
In a conventional solar battery, an internal electrical field is generated between P-N connecting members of a semiconductor layer. Impingement of light upon the solar battery develops electron/electron hole pairs. The electrons collect on the N side, with the electron holes formed on the P side. With an external load connected, electric current flows from the P side toward the N side. Through this process, solar batteries are able to convert light energy into usable electrical energy.
In recent years, solar batteries have been made using spherical semiconductors. Spherical semiconductors typically have a diameter of less than 1 mm and may be made from single crystals, or the like. Circuit patterns are formed on the surfaces of the spherical semiconductors.
An example of a conventional solar battery using spherical semiconductors is shown in FIG. 15 at 10. The solar battery 10 consists of an array of spherical semiconductors 12 which are connected together utilizing a conductive board 14, which in this case is shown to be aluminum foil, or the like. Each of the spherical semiconductors 12 has a primary conductive skin 16 which envelops a secondary conductive core 18. The spherical semiconductors 12 are placed in an opening 20 in the conductive board 14 so as to project from opposite sides 22 and 24 of the board 14. A portion of the skin 16 is removed from the spherical semiconductor 12 on the side 24 of the board 14. An insulating layer 26 is formed against the core 18 which is exposed where the external skin 16 is removed. A portion of the core 18 and insulating layer 26 is removed at 28 so as to form a flat surface 30 which can be connected to a secondary conductive member 32, which in this case is aluminum foil. The surface 30 is connected in a high quality, ohmic manner to the conductive member 32.
It is difficult to maintain a precise relationship between the semiconductors 12 and the conductive board 14, insulating layer 26, and secondary conductive member 32 throughout the entire area of the solar battery 10. Variation in the relationship of these elements may alter the operating characteristics of the semiconductors 12 and the performance of the battery 10.
Additionally, the manufacture of the solar battery 10 may involve multiple steps and processes. Manufacture may thus be relatively complicated. As a result, the costs attendant such manufacture may also be high.
In one form, the invention is directed to a solar battery having a board with a surface with a plurality of spherical segments projecting from the board surface. A primary electrode layer is provided on the board surface and the plurality of spherical segments. A semiconductor layer is provided on the primary electrode layer and has P-N connecting members. A secondary electrode layer on the semiconductor layer is made up of a translucent material.
In one form, the semiconductor layer is directly against the primary electrode layer and the secondary electrode layer is directly against the semiconductor layer.
The plurality of spherical segments may be arranged in rows.
The board may be made from an insulative material, such as glass or resin.
The board may be sufficiently flexible to be placed into a rolled form.
The board made be made from a conductive material, such as copper. In one form, the board is made from metal that defines the primary electrode layer.
The primary electrode layer may be made from chrome having a thickness on the order of 1 xcexcm.
The secondary electrode layer may be made from transparent indium tin oxide (ITO).
The semiconductor layer may include a positive amorphous silicon layer and a negative amorphous silicon layer.
The spherical segments may be formed as one piece with the board or separately placed on the board.
In one form, the spherical segments are each part of a sphere having a diameter on the order of 1 mm.
In the event a metallic board is used, a contact metallic layer may be placed on the metallic board under the secondary electrode layer. The contact metallic layer may be Nixe2x80x94Au.
The board surface may be embossed to define the plurality of spherical segments.
The positive and negative amorphous silicon layers may be formed using a CVD method.
The positive amorphous silicon layer may be formed through thermal decomposition using a silane mixture containing boron.
The negative amorphous silicon layer may be formed through thermal decomposition using a silane mixture containing phosphorous.
The secondary electrode layer may be applied using a sputtering method.
The board may be made from a polyimide film.
A collector may be provided over the secondary electrode layer between the spherical segments.
The invention is also directed to a method of treating a board for a solar battery. The method includes the steps of directing a first board having a surface with a plurality of spherical segments projecting from the first board surface through a first chamber containing a first reactive gas and directing the reactive gas at the first board in a plurality of directions in the first chamber to form a first layer on the board surface and the spherical segments.
The first board may be joined with a second board having a plurality of spherical segments projecting from the second board surface. The second board may be directed together with the first board through the first chamber so that reactive gas is directed at the second board in a plurality of directions in the first chamber.
In one form, each of the first and second boards has a back surface, facing oppositely to its respective surface with the plurality of projecting spherical segments thereon. The step of joining the first board with the second board may involve joining the back surfaces of the first and second boards.
The method may further include the steps of directing the first board into a second chamber and drawing the first reactive gas out of the second chamber.
The step of drawing the first reactive gas out of the second chamber may involve generating a low pressure region outside of the second chamber and drawing the first reactive gas from the second chamber into the low pressure region.
The method may further include the steps of directing the first board into a third chamber containing a second reactive gas after directing the first board into the second chamber and directing the second reactive gas at the first board in the third chamber to form a second layer over the first layer.
The first layer may be at least a part of a semiconductor layer.
The first board may be passed through a first conduit in the first chamber. The first conduit has a central axis and a peripheral wall with openings therethrough through which the first gas passes as it is directed against the first board.
The method may further include the step of directing the first reactive gas around the central axis as the first reactive gas is directed at the first board.
The plurality of openings in the peripheral wall may have central axes that are non-parallel to the central axis of the first conduit.
In one form, the first board moves in a first direction through the first chamber and at least one of the plurality of openings is oriented so that the first gas is directed generally in the first direction.
The first board may be passed through a second conduit in the second chamber with the second conduit being made from a porous material.
In one form, the first board is flexible. The method may include the step of placing the first board into a rolled form.
The first layer may be made from a positive amorphous silicon.
The first layer may be made from a negative amorphous silicon.
In one form, the porous material is produced through sintering of at least one of ceramic, resin and metallic powder.